1. Field of the Invention
The present invention relates generally to polymer compositions and, more particularly, to biodegradable polymer compositions, methods for making same, and articles therefrom.
2. Description of the Related Art
Starches and modified starches have been the focus of considerable research interest in attempts to use these as fillers in order to decrease polymer costs and to use polymers that are biodegradable. Several recent examples, U.S. Pat. No. 5,384,187, issued Jan. 24, 1995, to inventors Uemura et al., U.S. Pat. No. 5,391,423, issued Feb. 21, 1995, to inventors Wnuk et al., and U.S. Pat. No. 5,412,005, issued May 2, 1995, to inventors Bastioli et al., all represent domestic and foreign based attempts to achieve biodegradable polymer compositions in which natural polymers such as starches have been added to hydroxy-functional polymers.
Recent biodegradable polymer compositions have included a starch or a modified starch and a hydroxy-functional polymer. An example of such a biodegradable polymer composition is disclosed in U.S. Pat. No. 5,852,078, issued Dec. 22, 1998, to inventors Willett et al. This biodegradable polymer composition includes the use of granular starch and thermoplastic poly(hydroxy ester ethers)(PHEE) made with various difunctional acids such as adipic acid. However, uses of this composition may be extremely limited due to the low glass transition temperature of the PHEE made with adipic acid. Most articles formed from this composition easily softened and lost their shape at high temperatures of up to and more than 100xc2x0 C.
Further, it is known to mix starch with a thermoplastic polyester such as poly(lactic acid) (PLA). It is also known that such a mixture is immiscible and any resultant article formed is brittle with poor material properties. Therefore, there is a need in the art to provide polymer compositions with hydroxy-functional polymers and thermoplastic polyesters that are useful in the manufacture of biodegradable plastics, but which are easily prepared and processed into articles.
Accordingly, the present invention is a polymer composition. The polymer composition includes a first component being a hydroxy-functional polymer, a second component being a natural polymer and a third component being a thermoplastic polyester. The first component, second component and third component are compounded to form the polymer composition.
Also, the present invention is an article. The article includes a first component being a hydroxy-functional polymer, a second component being a natural polymer and a third component being a thermoplastic polyester. The first component, second component and third component are compounded to form a polymer composition which is processed into the article.
Further, the present invention is a method of making a polymer composition. The method includes the steps of providing a first component being a hydroxy-functional polymer, providing a second component being a natural polymer and providing a third component being a thermoplastic polyester. The method includes the steps of compounding the components to form a polymer composition.
The polymer compositions of the present invention are biodegradable and useful in various processes such as molding, extruding and casting to form molded articles and extruded sheets. The hydroxy-functional polymer may be as described by U.S. Pat. No. 5,171,820, issued Dec. 15, 1992, to inventors Mang et al., U.S. Pat. No. 5,496,910, issued Mar. 5, 1996, to inventors Mang et al., and PCT application published as International Publication No. WO 97/23564, on Jul. 3, 1997, to inventors Mang et al. Natural polymers for mixture with the hydroxy-functional polymers include polysaccharides, modified polysaccharides, naturally-occurring fibers, and particulate fillers. Particularly preferred as the natural polymer are starches. The thermoplastic polyesters for mixture with the natural polymers and hydroxy-functional polymers include poly(lactic acid)(PLA) and poly(caprolactone)(PCL).
One advantage of the present invention is that new polymer compositions are provided which are useful in the manufacture of biodegradable plastics. Another advantage of the present invention is that a method is provided of making such polymer compositions. Yet another advantage of the present invention is that the polymer compositions contain starch and a hydroxy-functional; polymer such as poly(hydroxy ester ether)(PHEE) and a thermoplastic polyester such as poly(lactic acid) (PLA) or poly(caprolactone) (PCL). Still another advantage of the present invention is that the method compounds the composition in at least one compounding step. A further advantage of the present invention is that the compounded composition is pelletized for further processing in various processes such as injection molding. Yet a further advantage of the present invention is that the polymer compositions are biodegradable and allow molded items to be formed such as planter pots, disposable razors, cutlery, pen casings, etc.
Other features and advantages of the present invention will be readily appreciated as the same becomes better understood after reading the subsequent description, examples and the appended claims.